Human skeletal remains can be used to identify the race to which the individual belongs by careful examination of certain discriminating features. The bones of human body, particularly cranial and facial bones, have underwent various changes over the period of time due to different modes of living, nutrition, environment, lifestyle. On the bases of these distinguishing features physical anthropologists have classified humans into three races-Caucasoids, Mongoloids and Negroids. The pioneers in this field include Vesalius, J.F Blumenbach and Franz Boas. These features of racial classification are of huge forensic importance as they can be used to estimate the race of skull recovered from crime scene which can give an insight to forensic anthropologists as to which direction the investigation should lead. Let us study these features of racial classification in detail.
Cephalic index is a metric feature that has been extensively used to categorize human skull into various. It is based on cranial measurements and is of the following types:
1-Horizontal Cephalic Index (HCI): It is defined as the ratio of maximum width of skull above ear (biparietal length) to the maximum length of skull (occipito-frontal length or glabella-inion length) multiplied by 100.
HCI% = (Max. biparietal length/ Max. length of skull) × 100
On the basis of horizontal cephalic index skulls can be classified into three categories:
- Brachycephalic: HCI greater than 80.9
- Mesocephalic: HCI between 76.0 and 80.9
- Dolichocephalic: HCI less than 76.0
Picture 1&2: Measurement of cephalic index and skull shapes on the basis of different values of cephalic indices.
2-Vertical Cephalic Index (VCI): It is defined as the ratio of maximum auricular head height (vertical distance between external auditory meatus and bregma i.e. point of intersection of coronal and sagittal suture) to the maximum length of skull (glabella-inion length) multiplied by 100.
VCI% = (Max. auricular head height/ Max. length of skull) × 100
On the basis of vertical cephalic index skull can be categorized as:
- Hypsicephalic: VCI greater than 63.0
- Orthocephalic: VCI between 58.0 and 62.9
- Chamaecephalic: VCI less than 58.0
3-Transverse Cephalic Index (TCI): It is defined as the ratio of maximum auricular head height to the maximum width of skull above ear multiplied by 100.
TCI% = (Max. auricular head height/ Max. cranial width) × 100
On the basis of transverse cephalic index skull can be classified into:
- Acrocephalic: TCI greater than 85.0
- Metriocephalic: TCI between 79.0 and 84.9
- Tapeiocephalic: TCI less than 79.0
Facial index is another important metric feature that can be used by forensic anthropologists to aid in racial identification. It is generally used in combination with cephalic index. Facial index is expressed in the form of Morphological Facial Index which is defined as the ratio of morphological facial height (linear distance between nasion and gnathion) to bizygomatic distance multiplied by 100.
Morphological Facial Index (MFI) = (Morphological facial height/bizygomatic width) × 100
On the basis of facial index faces are classified as:
- Hyper-euryproscopic: very broad face, MFI less than 80
- Euryproscopic: broad face, MFI between 80-84.9
- Mesoproscopic: round face, MFI between 85-89.9
- Leptoproscopic: long face, MFI between 90-94.9
- Hyper-leptoproscopic: very long face, MFI greater than 95
Picture 3: Measurement of morphological facial index.
Brachial index is a postcranial metric feature used for racial classification. It is defined as the ratio of maximum length of radius to the maximum length of humerus multiplied by 100.
Brachial index (B.I) = (max. length of radius/max. length of humerus) × 100
Maximum length of radius: It is defined as the maximum distance between most proximal point on the head to the tip of styloid process.
Maximum length of humerus: It is defined as the maximum distance between the most superior point on the head of humerus to the most inferior point on trochlea.
Crural index is defined as the ratio of maximum length of tibia to the maximum length of femur multiplied by 100.
Crural index (C.I) = (max. length of tibia/max. length of femur) × 100
Maximum length of tibia: It is defined as the maximum distance between the articular surface of lateral condyle to the tip of medial malleolus.
Maximum length of femur: It is defined as the maximum distance between the distance from the most superior point on the head of femur to a plane drawn along the inferior surfaces of distal condyles.
Metric and Non-metric features of various races and populations
- Tall skull, longer as compared to its breadth
- Sloping forehead as compared to mongoloids or negroids
- Orthognathous face with round orbits
- Retreating zygomas
- Mastoid process narrow and relatively more pointed than negroids or mongoloids
- Maxillary lateral incisors are of diminished size, overbiting is common
- Carabelli’s cusp is relatively more common in maxillary molars
- Bucco-lingual flattening of mandibular second premolars
- Long, narrow, and parabolic dental arch
Picture 4: A female caucasoid skull.
- Broader and round skull, medium in height
- Flat face with projecting zygomas
- Moderate alveolar prognathism
- Orbits are round and circular
- Mastoid process is wide and vertical
- Overbiting is absent among incisors
- Occlusal wear and tear of incisors is a characteristic feature of mongoloid
- Teeth are relatively largest as compared to negroids or caucasoids
- Shovel-shaped incisors
- Elliptical dental arch
- Extra distal root on mandibular first molars
- Incisors have shorter roots, roots of molars are mostly fused
Picture 5: A typical mongoloid skull.
- Longer and narrower skull, low in height
- Occipital area is rounded
- Strong alveolar and facial prognathism
- Rectangular shaped orbits
- Receding zygomas
- Nasal bones are strong and heavy, small/medium in size, wide nasal apertures
- Wide and hyperbolic dental arch
- Mastoid process has very small tubercle and obliquely inclined
- Crenulated occlusal surface of molars
- Extra cusp between the distal and mesial lingual surfaces of mandibular first molar
Picture 6: A negroid skull (anterior and lateral view)
Picture 7: Comparative view of skulls of caucasoids, mongoloids and negroids.
|Cephalic index||medium dolichocephalic||brachycephalic||dolichocephalic|
|Incisor shape||normal blade-like||shovel-shaped||blade-like|
|Nasal aperture||narrow and projecting||small||wide|
Table 1: Various cranial and facial features of caucasoids, mongoloids, and negroids
1-ILAYPERUMA, I. Evaluation of cephalic indices: a clue for racial and sex diversity. Int. J. Morphol., 29(1): 112-117,2011
2-Thoudam Bedita Devi et al. FACIAL MORPHOLOGY AND FACIAL INDEX: A STUDY ON SECULAR TREND OF MEITEI MALE POPULATION OF BISHNUPUR DISTRICT, MANIPUR, INDIA. Int J Anat Res 2016, 4(4):3279-83. DOI: 10.16965/ijar.2016.461
3-Reina V. Garcia, THE BRACHIAL AND CRURAL INDICES OF MODERN NORTH AMERICAN POPULATIONS, 2015.
4-Blumenfeld, Jodi (2000) “Racial Identification in the Skull and Teeth”, Totem: The University of Western Ontario Journal of Anthropology: Vol. 8: Iss. 1, Article 4